Electromechanical device



w; R. HARRY 9 ELECTROMEGHANICAL DEVICE Filed 061;. 15, 1941 2Sheets-Sheet 1 [-76.2 26 15:5? l I I:

r I 1 r 21- I I I I l INVENTOR W R. HA RR) W. R. HARRY 94 ,75

Jufly 2, ELECTROMEGHANICAL DEVICE Filed Oct. 15, 1941 2 Sheets-Sheet 2INVENTOR I By W RHARRV Patented July 23, 1946 2,404,375ELECTROMECHANICAL DEVICE William R. Harry, New York, N. Y., assignor toBell Telephone Laboratories, Incorporated, New York, N. Y., acorporation of New York Application October 15, 1941, Serial No. 415,013

This invention relates to electromechanical devices and, moreparticularly, to submarine signal detectors or microphones.

An object of the invention is to improve the structure and the operatingperformance of submarine signal detectors.

In accordance with the invention, the submarine signal detector is ofthe pressure gradient type, that is, its signal wave or under waterdisturbance responsive element is caused to move as a result of thepressure gradient established between different portions thereof by thesignal wave. The

movable element may comprise an annular member disposed in an annularair-gap and exposed on all its surfaces to the water, but presenting apair only of annular parallel planar surfaces on which the signal wavemay act. The annular member comprises a spool having a peripheralclosure member or ring. The annular member is supported by a pluralityof edge-stiffened flexible members, or by a plurality of longitudinallystifiened, damped flexible members, that permit movement of the windingmember in two directions only, 180 degrees apart. Since the signalresponsive element of the device is exposed to the water on all sides,the device does not require any means to compensate for the effect ofhydrostatic pressure. The planar surfaces of the signal responsiveelement are exposed to the water on opposite sides of a plate polemember having a central opening in which a second pole member ispositioned to form the annular gap in which the signal responsiveelement is located.

A more complete understanding of this invention will be derived from thedetailed description that follows, read with reference to the appendeddrawings, wherein:

Fig. 1 illustrates how a microphone embodying the features of thisinvention may be suspended or immersed in a liquid medium, for example,water;

Fig. 2 is a side elevational view of a submarine signal detector ormicrophone constructed in accordance with the invention;

Fig. 3 represents a cross-sectional view of the device of Figs. 1 and 2taken along the lines .3-3 of Fig. 2;

Fig. 4 represents another cross-sectional view of the device of Figs. 1and 2 taken along the lines 4-4 of Fig. 2;

Fig. 5 is a bottom plan view of the device of Figs. 1 and Fig. 6 is anenlarged view of the central portion of the device of Fig. 2 partly insection and 6 Claims. (Grin-4,86)

ill

partly broken away to show details of construction more clearly;

Fig. '7 is a partial section of the central portion of the device ofFigs. 1 and 2 with the annular member removed from the air-gap;

Fig. 8 is an enlarged showing in perspective of the signal wave. ordisturbance'responsive element of the device of Figs. 1 and 2, partlybroken away and partly in section, to show details, of its constructiontogether with the spring supporting means provided to locate and supportthe wave responsive element in an air-gap; and

Fig. 8A shows another construction for the spring supporting means forlocating and sup-. porting the wave responsive element in the airgap.

The invention is disclosed as embodied in 'a submarine signal detectoror microphone Ill. The microphone comprises a centrally locatedannularplate pole member II and a symmetrically shouldered center polemember l2 each of magnetic material. The inner diameter of theannular'projectingportion l3 of the plate pole and the outer diameter ofthe annular projecting portion M of the center pole are such that theypre sent spaced parallel pole faces defining an annular air-gap IS. Thepole members are coaxial and are maintained so by the annular plate l5containing elongated apertures-or slots l1. 7

tension 24 at its other end. Each extension 22 projects through apassage in the plate'member and threads into a recess 23 whereby thestuds and the plate member are rigidly united. The extensions 21, 24extend through passages at the outer ends of the symmetrically spacedarms or branches 25 of the yoke and are rigidly unitedthereto by thefastening members or nuts 28; Cylindrical permanent magnet members 21are clamped, bypressure exerted by the nuts 25, rigidly between eachyoke and the center pole l2, like poles of the magnet members beingadjacent the center pole.

The signal wave or disturbance responsive element of the microphonecomprises an annular element or coil 39 supported and positioned irrt-heair-gap l5 by a plurality of symmetrically locatedspring members 3 I.The element 30 comprises an annular spool or frame 32 of non-magneticmaterial having a peripheral annular groove or channel containing amultiturn winding 33 of small insulated wire. The frame is provided withpassages for the ends 34 of the winding, which are terminated at theterminal strips 35 supported on and insulated from the plate polemember. The winding is confined and sealed within the frame channel by atightly fitting peripheral closure or annulus 35 of non-magneticmaterial. The closure 36 may be omitted if, after the wire is wound inthe channel, it is vacuum impregnated in a Bakelite varnish medium.

Each spring member 3! comprises a strip of spring metal having aclamping portion 41 spaced from one surface of the plate pole by aspacer 31, and clamped against the spacer 31 by a plate 48 and screw 49,an L-shaped portion 38 whose horizontal leg 50 is suitably fastened toan annular planar surface of frame 32, and an intermediate stifi'enedportion 39 stiffened by virtue of the angular edge portions 40. Thesespring members provide a flexible support for the element 30, enablingit to move in two directions only, 180 degrees apart, with its lateralsurfaces moving substantially parallel to those of the pole faces. Fig.8A shows another construction of spring member that may be utilized tolocate and support the member 30 in its air-gap. It comprises a, stripof spring metal having a clamping portion 41', an L-shaped portion 38'whose horizontal leg 50' is adapted to be secured to the lower annularsurface of frame 32, and an intermediate stiffened portion 39',stiffened by virtue of the elongated boss or ridge 60. A sleeve ofdamping material, for example, of rubber, fits around the portion 39'.The clearance of space between the lateral surfaces of the element 30and the pole faces is so small that, although Water may flowtherethrough, signal waves or disturbances to which the microphone isintended to be responsive are presented with a very high impedance andhence are excluded. The winding 33 normally is located in the regionbetween the projecting portions l3, M of the pole members. Washermembers M44 are fastened to the horizontal surfaces of the portions I3,I4 to confine the action of the water and of the signal waves ordisturbances to the parallel upper and lower, annular planar surfaces ofthe element 30.

In a microphone constructed in accordance with this invention and of theproportions substantially those of Figs. 2 to 5, the magnet members 21were of an aluminum-nickel-cobalt steel alloy (Al-10%; Ni-17%; (Jo-12%;Cu-6%; Fe and C balance) the pole members, studs and yokes were ofSwedish steel; the spool and the peripheral closure of the element 30were of a plastic, and the winding 33 of 130 turns of No. 33 B. and S.enamel-coated aluminum wire; the spring supports 3! were of phosphorbronze shaped from strip material approximately .002 inch in thicknessand one-eighth inch in width. The air-gap was .125 inch wide, and theprojecting portions l3, Id of the pole members were approximately .125inch in thickness. The mass of the element 30 and of the spring supports31 was proportioned to be approximately equal to the radiation mass ofthe water. The flux density at the pole faces was of the order of 3000gauss.

The microphone described may be used in a liquid medium, and,specifically, in water to detect marine or submarine signal Waves ordisturbances over a broad band of frequencies, for

example, up to 20,000 to 30,000 cycles per second. It may also beemployed as a standard microphone for calibrating microphones of similaror of different construction intended for use in water.

The microphone described is of the pressure gradient type, i. e., itssignal responsive element 30 responds to the pressure gradient between,or the difierence in pressures established on, its parallel upper andlower surfaces by a signal wave or disturbance incident on themicrophone. The coil or element 30 is completely exposed to the water sothat the signal wave has access at least to the parallel portionsexposed on opposite sides or surfaces of the plate pole member; becauseof the proportions of the clearances between the coil and the polefaces, the signal wave is not effective on the lateral surfaces of theelement 30, and a signal wave originating on one side of the plate polemember must travel around the latter to be effective on the othersurface of the element 30. If the signal wave should be incident on themicrophone from such a direction that the portions of the wave acting onthe upper and lower surfaces of the element 30 are in phase, the elementremains stationary. If, however, the portions of the signal wave actingon the surfaces of the element 30 are out of phase, the coil or elementwill be caused to move to an extent determined by the intensity and themagnitude of the difference in phases of the signal wave on the twosurfaces. The microphone of the invention has a directional responsecharacteristic. This characteristic, it is evident, may be takenadvantage of in arrangements in which it is desired to maintain themicrophone in a stationary or in an adjustable position. Movement of theelement 30 in the air-gap in response to signal waves or disturbances inthe frequency range to which the microphone is responsive, generatescurrents corresponding thereto in the winding 33 which currents may bedetected or translated in suitable observation equipment to which themicrophone may be connected over the wires 55.

Although this invention has been disclosed with reference to a specificembodiment, it is not restricted thereto, but is of a scope evidenced bythe appended claims.

What is claimed is:

1. A microphone for use in a liquid wave transmission medium, comprisingmagnet structure providing a radial flux across an annular air-gap, asignal wave responsive element to be actuated directly by the signalwave disturbance in the medium and exposed on all of its surfaces tosaid medium, and means to mount said element for translational movementin said magnetic field, said element comprising an annular member havinga peripheral channel containing a multiturn winding.

A microphone for use in a liquid wave transmission medium, comprisingmagnet structure providing a radial flux across an annular air-gap, asignal wave responsive element to be actuated directly by the signalwave disturbance in the medium and exposed on all of its surfaces to themedium, and means to mount said element for translational movement insaid magnetic field, said element comprising an annular member having aperipheral channel containing a multitui'n winding and a peripheralclosure member confining said winding in said channel.

3. A microphone for use in a liquid wave transmission medium, comprisingmagnet structure providing a radial flux across an annular air-gap, asignal wave responsive element to be actuated directly by the signalWave disturbance in the medium and exposed on all of its surfaces to themedium, means to mount said element for translational movement in saidmagnetic field, said element comprising an annular member having aperipheral groove containing a multiturn winding, and means from whichsaid element is supported, said mounting means comprising a plurality offlexible members intermediate the support means and said element andsecured to each. 4. A microphone for use in a liquid wave trans missionmedium, comprising a plate pole member having a central opening, asecond pole member positioned in said central opening and forming anannular air-gap with the plate member, a source of magnetic flux forsaid pole members to establish a magnetic field across said air-gap, asignal wave responsive element to be actuated directly by the signalWave disturbance in the medium and exposed on all its surfaces to themedium and comprising an electrical conductor positioned in saidair-gap, and means to support said element in said air-gap for movementthere- 5. A microphone for use in a liquid Wave transmission medium,comprising a plate pole member having a central opening, a second polemember positioned in the central opening and forming an annular air-gapwith the plate member, a f

source of magnetic flux for said pole members to establish a magneticfield across said air-gap, a signal wave responsive element to beactuated directly by the signal wave disturbance in the medium andexposed on all its surfaces to the medium and comprising an electricalconductor positioned in said air-gap, and a plurality of flexiblemembers extending between said plate member and said element to supportthe latter in the air-gap for movement therein substantially in twodirections only degrees apart.

6. A microphone for use in a liquid wave transmission medium, comprisinga plate pole member having a central opening, a second pole memberpositioned in the central opening and formfor movement thereinsubstantially in two directions only 180 degrees apart.

WILLIAM R. HARRY.

